Key events in the Cambrian
-550 —
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-540 —
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-530 —
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-520 —
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-510 —
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-500 —
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-490 —
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Stratigraphic scale of the ICS subdivisions and Precambrian/Cambrian boundary.
Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia.[1] Neither the upper nor lower boundary have yet been defined by the International Commission on Stratigraphy.[2] Proposals for the lower boundary are the appearance of Small Shelly Fossils, an archaeocyathid species or the mollusc Watsonella crosbyi around 529 million years ago.[2] The proposed upper boundary might be the first appearance of trilobites around 521 million years ago.[2]
Possible candidates for a GSSP include the first appearance of Watsonella crosbyi in the Zhujiaqing Formation in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform.[3]
Palaeontology[edit]
Agnathans[edit]
Dinocarididans[edit]
References[edit]
- ^ Kouchinsky, Artem; Bengtson, Stefan; Missarzhevsky, Vladimir V.; Pelechaty, Shane; Torssander, Peter; Val'kov, Anatolij K. (24 September 2001). "Carbon isotope stratigraphy and the problem of a pre-Tommotian stage in Siberia". Geological Magazine. 138 (4). doi:10.1017/S0016756801005684.
- ^ a b c "GSSP List ICS". ICS. Archived from the original on 15 November 2012. Retrieved 9 November 2012.
- ^ Li, Guoxiang; Zhao, Xin; Gubanov, Alexander; Zhu, Maoyan; Na, Lin (1 April 2011). "Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2". Acta Geologica Sinica - English Edition. 85 (2): 309–319. doi:10.1111/j.1755-6724.2011.00400.x. Retrieved 10 November 2012.
